Research Report ZETJET-Aircraft Engines aviation can reduce cost of transport by up to 70% UAV 1 click picture for video test rig click picture for video UAV 2- click picture for video ZETJET AG Bahnhofplatz 3 6460 Altdorf Schweiz +41 55 420 30 03 www.zetjet.ch
Page 1 Summary Less fuel per tonne-kilometre is the goal of the development. Optimization of aircraft engines makes them larger and heavier, thus increasing weight and drag of the aircraft. Therefore, a significant part of the advantage from engine optimization is lost in flight conditions. This is a general goal conflict of aircraft optimization. In order to circumvent it, we need a new way of thinking about jet propulsion: Airplane, engine, and air are a single system for optimization. Then suddenly, there are new solutions for propulsion. ZETJET can significantly reduce the fuel requirements for a given flight profile. Using the range formula of Breguet, we can see the potential of the new approach. Less fuel for the engine increases the payload of the aircraft. The cascade effect then reduces the cost of the transportation task. The aircraft can carry more payload with less fuel, thus cutting transport cost. Depending on the range, the effect is astonishing (see chapter 5.4): Long range 15 000 km distance o Fuel requirements drop by 34% o Payload per flight increases by 120% o Cost as fuel per ton of freight decreases by 70% Medium range 5 000 km distance o Fuel requirements drop by 38% o Payload per flight increases by 27% o Cost as fuel per ton of freight decreases by 50%. Modern commercial aircraft have two or four engine nacelles under their wings. The engines are getting larger, and the nacelles produce more drag. However, this could be different. Every cyclist knows that there is an advantage to cycle behind someone else: The drag becomes lower, and the cyclist needs less energy to keep up the speed. This is the simple idea behind ZETJET: Put the engines behind the fuselage of the aircraft and remove nacelles from the wings. This minimizes the drag of all engines. The structure of the wing is relieved from the engines, this saves weight, and the inflow to the engine provides a secondary flow with some additional thrust. This is new. ZETJET engines are becoming more efficient with increasing speed. This is not part of current jet engines theory. We entered new science territory doing basic research. However, our experiments demonstrate the effect with no doubt. In the lab, a ZETJET engine needed 30% less power than a conventional engine for the same transportation task. The report describes the test arrangements and the results of the measurements. It shows new approaches for optimizing transport by aviation.
Page 2 Summary... 1 1 Situation... 3 2 Innovation ZETJET... 6 3 Experimental set-up... 8 3.1 Test engines... 8 3.2 Carousel test rig... 9 4 Efficiency analysis... 10 4.1 Test approach... 10 4.2 Configurations A / B / C... 11 4.3 Results of configuration A... 12 4.4 Results of configuration B... 13 4.5 Results of configuration C... 14 4.6 Comparison of configurations B / A... 15 4.7 Comparison of configurations C / A... 16 4.8 Comparison of configurations C / B... 17 5 Discussion... 18 5.1 Results... 18 5.2 Error analysis... 19 5.3 Extrapolation... 19 5.4 Implications... 20 6 Outlook... 23 7 Conclusion... 24 7.1 Findings... 24 7.2 Acknowledgement... 24
Page 3 1 Situation According to current market studies, global air traffic is growing by about four percent per year, and it will double within a few years. At the same time, fuel consumption is increasing. Currently, global aviation burns some 300 million tons of kerosene per year, resulting in 1 150 million tonnes of CO 2. Due to rising prices, fuel is the largest cost factor of any airline. Depending on the oil price, fuel expenditures reach 25% to 30% of annual turnover already. Therefore, great efforts try to reduce the fuel requirements of aircraft. Engine Airplane Optimisation Components Engine Manufacturers optimize engines and measure fuel consumption per generated thrust (SFC = Specific Fuel Consumption). At cruise the best engines require more than 15 gram of kerosene per second to generate 1 000 Newton thrust (g/skn) Airplane manufacturers optimize airplanes and measure fuel consumption per payload distance. In 2015 fuel consumption was at a level of 23.5 litre per 100 ATK (ATK = Available Ton Kilometres). Today, different manufacturers develop engines and airplanes. The players follow two different strategies: Engine manufacturers try to generate more thrust using less fuel. They increase the mass flow of air and the pressure of the gas turbine. This reduces losses caused by jet flow and losses from thermal energy conversion of the gas turbine. Today the best engines reach an overall efficiency of some 38.5%. Airplane manufacturers try to increase the overall transport value using less fuel. They reduce the weight and drag of the aircraft. Weight reduction cascades into the design of the aircraft where less weight needs smaller wings, smaller wings need less thrust, and less thrust means smaller engines, again with less weight, and so on. Between 2000 and 2015, fuel consumption in aviation dropped from 55 litres to 35 litres per revenue ton kilometres (RTK).
Page 4 Due to the separation of engine and aircraft, the drag of the nacelle counted as part of the drag of the airplane. This creates conflicting goals when optimizing transportation by aircraft. Engine optimization increases the size, the weight and the drag of the nacelle, thus counteracting the efforts done by optimization of the airplane body and wings itself. Conflicting goals and effects The improvement of the first component leads to a disadvantage of the other, and the forecasts of fuel consumption by manufactures are always below the actual values obtained from flight: Airplanes actually need more fuel than expected. An analysis of existing databases shows the effect of the conflicts of optimization between engine and airplane: In 1995, Rolls Royce Trent 772 at cruise needed 16 gram kerosene per second and 1 000 Newton thrust (SFC = Specific Fuel Consumption in g/skn) Compared with the Trent 772, Rolls Royce optimized the new engine Trent 890 by increasing the bypass ratio from 4.89 to 5.74, and the pressure ratio from 36.8 to 42.7. In 1998, a Rolls Royce Trent 890 at cruise needed 15.8 g/skn. According to theory, the overall efficiency should have improved by some 6%. At flight, the efficiency increased from 35.3% to 36.2%. The real gain for the aircraft was less than 1%. Under the wing and in flight the engines require more fuel than on the test bench. The reason for this is the interdependency between engine and airplane and the nacelle of the engine. So far, nobody has reached a value below 15 g/skn in flight, and the actual research seems to reach an end. We have good reasons to assume, that the expected SFC improvements as announced for the next generation of jet engines are in fact out of reach.
Page 5 Database analysis Results: The development path is approaching a limit of SFC = 15 g/skn for 900 km/h. Example of the above analysis: 1995 Rolls Royce Trent 772 SFC = 15.9 g/skn at cruise 1995 Planning for Rolls Royce Trent 890 with SFC = 14.3 g/skn on test bench 1998 Rolls Royce Trent 890 SFC = 15.8 g/skn at cruise 2016 Announcement of Rolls Royce Ultra Fan for 2025 with SFC = 12.8 g/skn The forecasted fuel consumption is well below the real values in flight condition The efficiency announced for 2025 lies way outside of the trend line. Data base: Civil Jet Aircraft Engine Design and own calculations
Page 6 2 Innovation ZETJET In order to overcome the optimization conflict between airplane and engine, ZETJET shifts the design focus: Aircraft, engine, and air are the complete system, with dependencies between all components involved. Now, it is not to find the best engine or the best aircraft, but the lowest amount of fuel required for a given transportation task: Put a payload into a box, and move that box very fast through the air. The aircraft system then contains payload, fuselage, wings, engines, and air. Airplane Transportation Task Components of the system The payload needs a fuselage in order to store, protect, and move it The fuselage contains payload and needs wings to fly The wings lift and guide the airplane, and they produce drag Engines generate thrust and push the airplane fast through the air Air flows and causes forces and drag All components of the system travel inside the same air, interconnected. Now, the design task needs adjustment, and we structure the problem in a different way than before: The total drag of the engine and the nacelle belongs to the engine. The engine provides net thrust to a glider only. The propulsive air flow generated by the engine creates aerodynamic forces which need to be taken into account during integration of engine and airplane Old New Decomposition of system
Page 7 This approach results in a new engine model, where the engine first needs to push itself through the air. This requires thrust. Engine drag then reduces gross thrust, and the sailplane only receives net thrust for aircraft propulsion. old model - engine without drag new model - engine with drag Engine model It is clear, that the overall efficiency of the transport task depends on the net thrust available, and not on the gross thrust generated. It is of no practical use to build a highly efficient engine, but very large and heavy, which consumes most of its thrust to move itself through the air. It is also clear, that an integration of engine and airplane becomes optimal with little or no drag from the nacelle, so the gross thrust becomes equal to the net thrust. The engine drag is minimal, when it is located outside of the direct airflow, and placed behind the fuselage. Obviously, in such a design, the air cannot enter the engine from the front. This is the starting point for an innovative engine concept, where we put the engine behind the aircraft body. We compare the well-known engine concept (FANJET) with the new concept (ZETJET): FANJET ZETJET Thrust generation Features FANJET is a conventional jet engine as used in modern airplanes. Air flows in from the front into the engine, and it flows out as high-speed jet towards the back. This creates thrust propelling the airplane. ZETJET is an innovative engine placed behind the body of an airplane. First, air flows around the aircraft body, and then through aerodynamic profiles towards the propeller generating the jet. No nacelle has no drag, and the airplane is more efficient overall.
Page 8 3 Experimental set-up In order to measure the overall efficiency, we mount both engine concepts on a carousel test bench. We use model engines with off the shelf electric impellers. 3.1 Test engines FANJET ZETJET Test model FANJET Engine is placed outside of body Still air from the front Fast jet to the back ZETJET Engine is placed behind body Still air from the side Fast jet to the back Features Primary thrust from difference of momentum Primary thrust from air jet Secondary thrust from additional lift by aerodynamic profiles Nacelle is not part of the body Air plane receives net thrust Displacement is part of body Air plane receives gross thrust Air plane receives additional thrust FANJET-engines need to push their own nacelle through the air. This requires thrust. The remaining net thrust is available for the airplane. Experiment ZETJET-engines are in the slipstream behind the body. The airplane now receives the complete gross thrust. Additionally, the secondary airflow from the side generates extra thrust when passing through the aerodynamic profiles. The experiment compares two engine concepts. Both contain the very same electric impeller for propulsion. Different elements of the test bench represent drag resistance of an aircraft, like wings, body, and nacelle. The FANJET has a nacelle exposed to the airstream, while the ZETJET is integral part of the fuselage with very little additional drag. We measure the final speed of the test engines at a given power input.
Page 9 3.2 Carousel test rig Carousel test rig Properties Test rig Features Carousel test rig 14 m diameter 44 m circumference Short arm, 3 m length with counter weight up to 40 kg Long arm, 7 m length with test engines up to 10 kg Thrust experiments with electric impeller up to 10 kw electrical power Air drag experiments with drive motor up to 7 kw electrical power Speed up to 200 km/h Centrifugal load up to 50 g Carousels belong to the most cost effective test rigs for flow experiments under laboratory conditions. Test objects are moving through still air instead of hanging in a wind tunnel with air from a blower. Otto Lilienthal developed the theory of modern aerodynamics with the help of a carousel. The carousel built by ZETJET AG can operate up to a maximum speed of 200 km/h with experiments up to 10 kw power consumption of the engine. Using a wind tunnel for the same experiments would require a cross section of 1.5 m x 1.5 m and a fan accelerating the air to 200 km/h with a power consumption of 300 kw. The short arm represents some drag of the fuselage, and the long arm represents the wings. The FANJET has an external nacelle with additional drag, while the ZETJET is integral part of the airplane body. All experiments use the very same electric impeller mounted into one model or the other.
Page 10 4 Efficiency analysis For the analysis of the efficiency, we compare the speed reached and the power consumed using the very same electric impeller. The more efficient engine reaches more speed with the same power. Based on these measurements we calculate the efficiency advantage at the same speed. In the example below, we measure the final speed of two models at 6 kw power. Type A reaches a speed of 43 m/s. Type B is faster with 49 m/s. For 43 m/s, type B requires 4 kw only, which is a third less. Concept of the experimental set-up Example 4.1 Test approach To ensure comparable results, we place the two engines models FANJET and ZETJET in parallel at the end of the long arm, one above the other. The drag is the same for all tests. The very same electric impeller drives each engine model, first, inside the FANJET model, second, inside the ZETJET model. We measure the revolutions per minute (rpm) of the carousel and power consumption of the impeller motor at a fixed input voltage. RPM of the carousel and circumference gives velocity. By varying the input voltage from 20 to 48 Volts at 4 Volt steps, we obtain a number of data points for power and speed. Interpolation with cubic polynomials allows us to calculate the efficiency advantages. We measure three configurations: A. FANJET holds the electric impeller, ZETJET-model is empty and covered (body of airplane) B. FANJET-nacelle is empty, ZETJET holds the electric impeller with flow input uncovered and aerodynamic profiles can work (body of airplane) C. ZETJET-model without FANJET-nacelle (the nacelle and it s air drag is removed) Subsequently, the different combination of configurations B/A, C/A and C/B are compared.
Page 11 4.2 Configurations A / B / C All components of the carousel generating drag represent components of the airplane: The short arm of the carousel is part of the body of the airplane The long arm of the carousel represents the wings The ZETJET housing is part of the body of the airplane The FANJET housing is placed in form of an external nacelle in the air stream The pictures show all configurations measured. Subsequent chapters show results. The diagrams show all data points of measurements and polynomial interpolations as continuous line. Configurations A / B / C Properties Configuration A Configuration B ZETJET is empty aerodynamic profiles are covered, drag belongs to the body FANJET contains the electric impeller, air flows in from the front, jet is directed backwards Radius of propelling engine = 6.91 m ZETJET contains the electric impeller, aerodynamic profiles are working, drag belongs to the body, air flows in from the side, jet is directed backwards, engine is placed behind body Radius of propelling engine = 6.96 m FANJET casing is empty, no propeller, drag of empty nacelle remains as load Configuration C ZETJET contains the electric impeller, drag belongs to the body, air flows in from the side, jet is directed backwards Radius of propelling engine = 6.96 m FANJET nacelle is removed, no extra drag from FANJET
Page 12 4.3 Results of configuration A Configuration A: ZETJET empty/closed and FANJET propelling Results A Configuration A Measurements A measure M5814 - FANJET interploate U v P P (v) error P (v) Volt m/s Watt Watt % 48.00 39.65 5'531.04 5'533.44 0.04% 44.00 37.12 4'472.11 4'465.84-0.14% 40.00 34.37 3'493.61 3'496.57 0.08% 36.00 31.40 2'641.93 2'641.22-0.03% 32.00 28.22 1'904.80 1'911.38 0.35% 28.00 24.96 1'316.29 1'313.70-0.20% 24.00 21.56 854.86 849.01-0.68% 20.00 17.95 507.80 511.26 0.68% mean squared error 0.37% power measurement A M5814 FANJET engine with nacelle outside of body 8 data points with cubic interpolation motor voltage 48 V down to 20 V at -4V steps maximum speed = 39.65 m/s at 5 531 W interpolation P = P(v 3 ) mean squared error = 0.37%
Page 13 4.4 Results of configuration B Configuration B: FANJET empty and ZETJET propelling Results B Configuration B Measurements B measure M5813 - ZET+FAN interploate U v P P (v) error P (v) Volt m/s Watt Watt % 48.00 39.94 5'434.20 5'434.53 0.01% 44.00 37.03 4'362.18 4'361.03-0.03% 40.00 34.11 3'399.00 3'402.14 0.09% 36.00 31.05 2'572.90 2'564.92-0.31% 32.00 27.84 1'844.75 1'854.02 0.50% 28.00 24.49 1'272.70 1'271.41-0.10% 24.00 20.99 820.41 815.97-0.54% 20.00 17.49 481.10 483.22 0.44% mean squared error 0.33% Power measurement B M5813 ZETJET engine plus empty nacelle with drag 8 data points with cubic interpolation motor voltage 48 V down to 20 V at -4V steps maximum speed = 39.94 m/s at 5 434 W interpolation P = P(v 3 ) mean squared error = 0.33%
Page 14 4.5 Results of configuration C Configuration C: ZETJET propelling, no FANJET nacelle Results C Measurements C Configuration C Power measurement C M5812 ZETJET with FANJET nacelle removed 8 data points with cubic interpolation motor voltage 48 V down to 20 V at -4V steps maximum speed = 44.10 m/s at 5 422 W Interpolation P = P(v 3 ) mean squared error = 0.33%
Page 15 4.6 Comparison of configurations B / A B ZETJET propelling A FANJET propelling Calculations B/A Comparison B/A Both configurations show nearly the same drag. Discussion B/A At 45 m/s, ZETJET propulsion is some 6% more efficient than FANJET propulsion. The efficiency advantage of ZETJET increases with speed. With higher velocity of the airplane, ZETJET performs increasingly better than FANJET. This effect comes from additional thrust gained from the secondary airflow, which passes through the aerodynamic profiles. This is Energy Harvesting for aircraft propulsion. The empty nacelle causes unnecessary drag.
Page 16 4.7 Comparison of configurations C / A C ZETJET without nacelle A FANJET propelling Calculations C/A Discussion C/A Comparison C/A The empty nacelle of FANJET is expendable, and it becomes obsolete. The total airplane now has a lower drag. At 45 m/s, the propulsion with ZETJET is some 30% more efficient than the propulsion with FANJET. The efficiency advantage of ZETJET increases with speed. With higher velocity of the airplane, ZETJET performs increasingly better than FANJET. This effect comes from additional thrust gained from the secondary airflow, which passes through the aerodynamic profiles. This is Energy Harvesting for aircraft propulsion. Until now, no aircraft engine featured these characteristics.
Page 17 4.8 Comparison of configurations C / B C ZETJET without nacelle B ZETJET with empty nacelle Calculations C/B Discussion C/B Comparison C/B Relevant cross sections: ZETJET casing = 570 cm 2, FANJET nacelle = 220 cm 2, total = 790 cm 2. The removal of the nacelle reduces the drag relevant cross section by 220/790 = 27.8%. We measured a decrease of the drag by some 25%, which is in line with the expectations. Once in motion the difference between the two configurations remains stable and independent from speed. The previously identified efficiency gain is not achievable with a reduction of the drag alone. ZETJET-engines offer efficiency advantages, which increase with higher speed. Such a result is not possible with FANJET-engines, and such behaviour was previously unknown. This is the huge and still untapped potential of this breakthrough propulsion concept.
Page 18 5 Discussion 5.1 Results On the carousel, we measured three different engine configurations at constant power. The more efficient engine is faster at the same power. With each measurement, we obtained eight data points for speed and power. We then calculated the power consumed as function of velocity using cubic polynomials. This models the dependency between power consumption and speed correctly, and we get a numerical representation of the propulsion physics. The mean squared error between the measurements and the cubic polynomials is less than 0.4%. Without any doubt, our measurements show, that the efficiency advantage of ZETJET-engines over FANJET-engines does increase with velocity. With increasing speed, ZETJET utilizes energy from fuel better than FANJET. The efficiency factor increases with speed! This is new and previously unknown. Current propulsion theory of airplane engines cannot explain this feature. In comparison with the FANJET-model at a speed of 45 m/s, our ZETJET-model was more efficient by some 6%. However, a ZETJET-configuration allows us to eliminate the external nacelle of a FANJET, and to put the engine into the slipstream behind the fuselage. Then, at 45m/s, ZETJET was 30% more efficient than a comparable setup based on FANJET.
Page 19 5.2 Error analysis The measurement of the rpm of the carousel allows us to calculate the correct speed over ground (GS = Ground Speed), but the power consumption depends on the speed through the air (TAS = True Airspeed). The carousel induces a very small airflow (check video of the test-bench/carousel) so that there is a difference between GS and TAS of up to 5%. Due to the fact, that all three measured configurations use the very same electric impeller and the same pre-set voltages, the error induced by the difference between GS and TAS are affecting all measurement in the same small range. The comparisons are still valid. There may be a scaling error against speed; however, the basic nature of the efficiency characteristic remains unchanged. 5.3 Extrapolation We can extrapolate the cubic power polynomials beyond the velocity range measured. Although extrapolation requires great care, we can obtain some insight into the expected behaviour of the engines at higher velocity. The calculation shows an extrapolation up to 250 m/s (900 km/h). The trend lines show a further increase of the efficiency, and a limiting boundary value, which is plausible. With all due scepticism towards such an extrapolation, we can expect from the values shown in the diagram that a reduction of the fuel consumption by 40% is not impossible, and could be achieved. This is a result far beyond the possibilities of existing FANJET configurations. It comes from a new airplane design approach based on the ZETJET propulsion concept.
Page 20 5.4 Implications With the formula of Louis Charles Breguet, we can estimate the travel distance of any airplane. A more efficient aircraft engine needs less fuel. For a given aircraft, we can reduce the fuel on board in favour of the payload, or we can reduce the weight of the aircraft structure at constant payload. We determine the implications of the efficiency gains of a ZETJET-engine using two calculations based upon Breguet s formula: 1. The take-off weight remains constant. The fuel advantage allows a higher payload per flight. 2. The payload weight remains constant. The fuel advantage allows a lighter aircraft. The first table shows a model calculation with efficiency enhancements for medium and long distance aircraft, based on Airbus A320 and A380 models. The numbers for aircraft, fuel, and payload define the respective masses in tonnes. The calculation of advantages achieved relates to fuel savings, increase of payload, and savings of the specific operating costs as a ratio of the amount of fuel per ton of cargo. Efficiency Gain 0.0% 5.0% 10.0% 15.0% 20.0% 25.0% 30.0% 35.0% 40.0% 45.0% 50.0% SFC g/skn 16.00 15.20 14.40 13.60 12.80 12.00 11.20 10.40 9.60 8.80 8.00 long range aircraft 250.0 250.0 250.0 250.0 250.0 250.0 250.0 250.0 250.0 250.0 250.0 15'000 km fuel 250.0 240.4 230.5 220.3 209.9 199.2 188.2 176.9 165.3 153.5 141.3 payload 70.0 79.6 89.5 99.7 110.1 120.8 131.8 143.1 154.7 166.5 178.7 total 570.0 570.0 570.0 570.0 570.0 570.0 570.0 570.0 570.0 570.0 570.0 mass budget aircraft 43.9% 43.9% 43.9% 43.9% 43.9% 43.9% 43.9% 43.9% 43.9% 43.9% 43.9% fuel 43.9% 42.2% 40.4% 38.7% 36.8% 34.9% 33.0% 31.0% 29.0% 26.9% 24.8% payload 12.3% 14.0% 15.7% 17.5% 19.3% 21.2% 23.1% 25.1% 27.1% 29.2% 31.4% total 100.0% 100.0% 100.0% 100.0% 100.0% 100.0% 100.0% 100.0% 100.0% 100.0% 100.0% advantage fuel 0.0% -3.9% -7.8% -11.9% -16.0% -20.3% -24.7% -29.2% -33.9% -38.6% -43.5% payload 0.0% 13.8% 27.9% 42.4% 57.3% 72.6% 88.3% 104.4% 120.9% 137.9% 155.3% cost 0.0% -15.5% -27.9% -38.1% -46.6% -53.8% -60.0% -65.4% -70.1% -74.2% -77.9% medium range aircraft 40.0 40.0 40.0 40.0 40.0 40.0 40.0 40.0 40.0 40.0 40.0 5'000 km fuel 16.0 15.3 14.5 13.8 13.1 12.3 11.5 10.8 10.0 9.2 8.4 payload 22.0 22.7 23.5 24.2 24.9 25.7 26.5 27.2 28.0 28.8 29.6 total 78.0 78.0 78.0 78.0 78.0 78.0 78.0 78.0 78.0 78.0 78.0 mass budget aircraft 51.3% 51.3% 51.3% 51.3% 51.3% 51.3% 51.3% 51.3% 51.3% 51.3% 51.3% fuel 20.5% 19.6% 18.6% 17.7% 16.7% 15.8% 14.8% 13.8% 12.8% 11.8% 10.8% payload 28.2% 29.1% 30.1% 31.0% 32.0% 33.0% 33.9% 34.9% 35.9% 36.9% 37.9% total 100.0% 100.0% 100.0% 100.0% 100.0% 100.0% 100.0% 100.0% 100.0% 100.0% 100.0% advantage fuel 0.0% -4.5% -9.1% -13.7% -18.4% -23.1% -27.9% -32.7% -37.6% -42.5% -47.5% payload 0.0% 3.3% 6.6% 10.0% 13.4% 16.8% 20.3% 23.8% 27.3% 30.9% 34.5% cost 0.0% -7.6% -14.8% -21.6% -28.0% -34.2% -40.1% -45.7% -51.0% -56.1% -61.0%
Page 21 Because fuel consumption decreases, we can increase the payload. The operations cost are given by the fuel consumption per ton kilometre (ATK = available ton kilometres). With an efficiency gain of 30% to 40% through the engine, there is a tremendous impact on the aircraft. Long-Range 15 000 km distance o Fuel consumption drops by 25% 34% o Payload increases by 88% - 120% o Fuel cost per transported ton payload drop by 60% to 70% Mid-Range 5 000 km distance o Fuel consumption drops by 28% 38% o Payload increases by 20% - 27% o Fuel cost per transported ton payload drop by 40% to 50% The second model calculation shifts fuel savings of the propulsion system into a smaller and lighter airplane, which creates a cascading effect into the overall design of the aircraft (smaller tanks, smaller wings, smaller engines, and less structural weight). The payload of the aircraft remains constant. Efficiency Gain 0.0% 5.0% 10.0% 15.0% 20.0% 25.0% 30.0% 35.0% 40.0% 45.0% 50.0% SFC g/skn 16.00 15.20 14.40 13.60 12.80 12.00 11.20 10.40 9.60 8.80 8.00 long range aircraft 250.0 219.7 195.5 175.5 158.9 144.8 132.8 122.3 113.2 105.1 97.9 15'000 km fuel 250.0 211.3 180.2 154.7 133.4 115.4 99.9 86.6 74.8 64.5 55.3 payload 70.0 70.0 70.0 70.0 70.0 70.0 70.0 70.0 70.0 70.0 70.0 total 570.0 501.0 445.6 400.2 362.3 330.2 302.7 278.9 258.0 239.6 223.2 mass budget aircraft 43.9% 43.9% 43.9% 43.9% 43.9% 43.9% 43.9% 43.9% 43.9% 43.9% 43.9% fuel 43.9% 42.2% 40.4% 38.7% 36.8% 34.9% 33.0% 31.0% 29.0% 26.9% 24.8% payload 12.3% 14.0% 15.7% 17.5% 19.3% 21.2% 23.1% 25.1% 27.1% 29.2% 31.4% total 100.0% 100.0% 100.0% 100.0% 100.0% 100.0% 100.0% 100.0% 100.0% 100.0% 100.0% advantage fuel 0.0% -3.9% -7.8% -11.9% -16.0% -20.3% -24.7% -29.2% -33.9% -38.6% -43.5% aircraft 0.0% -12.1% -21.8% -29.8% -36.4% -42.1% -46.9% -51.1% -54.7% -58.0% -60.8% cost 0.0% -15.5% -27.9% -38.1% -46.6% -53.8% -60.0% -65.4% -70.1% -74.2% -77.9% medium range aircraft 40.0 38.7 37.5 36.4 35.3 34.2 33.3 32.3 31.4 30.6 29.7 5'000 km fuel 16.0 14.8 13.6 12.5 11.5 10.5 9.6 8.7 7.8 7.0 6.2 payload 22.0 22.0 22.0 22.0 22.0 22.0 22.0 22.0 22.0 22.0 22.0 total 78.0 75.5 73.2 70.9 68.8 66.8 64.8 63.0 61.3 59.6 58.0 mass budget aircraft 51.3% 51.3% 51.3% 51.3% 51.3% 51.3% 51.3% 51.3% 51.3% 51.3% 51.3% fuel 20.5% 19.6% 18.6% 17.7% 16.7% 15.8% 14.8% 13.8% 12.8% 11.8% 10.8% payload 28.2% 29.1% 30.1% 31.0% 32.0% 33.0% 33.9% 34.9% 35.9% 36.9% 37.9% total 100.0% 100.0% 100.0% 100.0% 100.0% 100.0% 100.0% 100.0% 100.0% 100.0% 100.0% advantage fuel 0.0% -4.5% -9.1% -13.7% -18.4% -23.1% -27.9% -32.7% -37.6% -42.5% -47.5% aircraft 0.0% -3.2% -6.2% -9.1% -11.8% -14.4% -16.9% -19.2% -21.5% -23.6% -25.7% cost 0.0% -7.6% -14.8% -21.6% -28.0% -34.2% -40.1% -45.7% -51.0% -56.1% -61.0%
Page 22 The cascading effect makes the aircraft structure lighter, this reduces fuel requirement, which lowers the take-off weight, etc. The same transport task needs less fuel, so the aircraft becomes lighter. As it becomes lighter, the cost of material decreases, as does the cost of purchasing and manufacturing. The final product can have at lower price, although the margin for the manufacturer increases. From the model calculation with constant freight and identical mass balance, we can see the results: Long-Range 15 000 km distance o Fuel consumption drops by 60% to 70% o Airplane weight (MTOW) drops by 47% to 55% o Fuel cost per transported ton payload drops by 60% to 70% Mid-Range 5 000 km distance o Fuel consumption drops by 40% to 51% o Airplane weight (MTOW) drops by 17% to 22% o Fuel cost per transported ton payload drops by 40% to 50% Both models use the same mass ratio for airplane structure weight, payload and fuel load. In reality, this is unlikely to be achievable. However, the simple calculations show that an optimization of the overall system (smaller airplane and wings, more efficient engines, no nacelle, payload, lower MTOW) can generate substantial savings. The savings expected increase with flight distance of the aircraft. The different approach makes it possible to identify an optimization potential that can cut fuel consumption in aviation by 50%. The greater the range of the aircraft, the more can be saved
Page 23 6 Outlook Our experiments show, that we can increase the efficiency of fuel far more than ever expected. In order to achieve such a huge efficiency gain, we need to optimize the overall system and utilize the connections between system components. We need to exploit the interdependencies between engine, airplane and air. Based on our configurations analysed, we can sketch new concepts for future airplanes A. Airplane today: FANJET with nacelles under wings B. First new generation: ZETJET replace FANJET under wings C. Second new generation: ZETJET behind body, wings without nacelle Configurations A / B / C Airplane A / B / C C - ZETJET behind body B - ZETJET in nacelle A - FANJET in nacelle
Page 24 7 Conclusion 7.1 Findings The results of our experiments show, that a proper integration and optimization of an airplane with the new ZETJET concept can achieve fuel savings far beyond previous belief: 1. There is no need for an external nacelle. A ZETJET engines can operate behind the fuselage of the airplane, reducing drag and saving fuel. Gross thrust is available for the propulsion of the airplane (glider). 2. The ZETJET engine can exploit a secondary airflow to generate additional thrust. The use of aerodynamic profiles is simple and cost effective. This is new. 3. The ZETJET engine shows an increase in efficiency with speed. This effect has a huge potential, it is new, and it needs further exploration. ZETJET-engines show characteristics far beyond current theories applied for the design of aircraft engines. We have ventured into unchartered waters and created first scientific evidence, that aviation industry can reduce fuel consumption by 50% or more. We can halve the fuel needs for aircraft, and decarbonizing of aviation becomes possible. Hydrogen/fuel cell/electric propulsion solutions for airplanes are now more likely. ZETJET engines and concepts are a breakthrough technology, and able to renew the aviation industry radically. 7.2 Acknowledgement The research was possible through funding by the Federal Office of Civil Aviation (FOCA) of Switzerland. We would like to thank FOCA for the support received.