LHR ENGINE
CHAPTER - 5 LNR ENGINE 5.0 INTRODUCTION The studies on the performance of the conventional engine are shown in Chapter - 4. The research is extended to conduct experiments so as to improve the performance of the engine in terms of Brake Thermal Efficiency. The need of the LHR Engine has been explained in the Chapter - 2. Accordingly, the modifications are taken-up for the engine considered in Chapter -4. The detailed modifications to piston crown are explained leading to LHR Engine. The experiments are conducted on the Engine with the better Bio-diesel Blend of each of the five Bio-Diesels. The detailed Methodology is explained in the following. 51 LHR ENGINE CONCEPT A brief concept of the LHR Engine is mentioned here before the experiments are conducted on the LHR Engine. The early IC Engines developers realized the advantage of increased combustion chamber temperatures. It is known fact that the efficiency theoretical cycle depends directly on the temperature difference between the hot and the cold portions of the engine cycle. If the combustion gas energy can be contained through the expansion cycle, then the efficiency of the engine can be increased. Such increase in the efficiency of Internal Combustion Engine is possible by generating the higher chamber temperatures and thus the LHR Engine concept has gained importance. In gasoline Engines, the thermal insulation will increase the wall temperature which will lead to unwanted detonation. Therefore, the insulation of the combustion chamber could be done only in Diesel Engine. In the process, the insulation of the combustion chamber is done by coating with ceramics such as Partially Stabilised Zirconia and Aluminum Titanate. Such insulations some times increase the temperature of cylinder walls leading to cooling issues.
5.1.1 Introduction to LHR Engine: The main purpose of a Low Heat Rejection is minimise the heat loss to the coolant by providing heat resistance in the heat flow to the Coolant. The heat generated inside the cylinder during chemical combustion of the fuel develops work by moving the piston downwards and some of the heat is lost to (i) cylinder walls, (ii) over come fiction, (iii) exhaust gases, (iv) cooling water, etc. Thus the load on the engine varies, the magnitude of the heat losses also vary. In this context, the theoretical adiabatic engine can be treated as a no-heat loss engine. But, it cannot become a practical engine without heat loss as mentioned above. 5.2 TURBO-CHARGING AND TURBO-COMPOUNDING The maximum power output from an Engine is limited and dependent on the amount of fuel burnt in the engine cylinder and hence the development of thermal energy. Therefore, the present researchers generally relaying to estimate engine performance based on the Brake Thermal Efficiency and the Specific Energy Consumption. If the induced air is compressed to higher density than the ambient, prior to entry to the cylinder, the engine develops less than that of the capacity to develop a maximum power. This is the primary purpose of supercharging. The supercharging can be achieved through (i) Mechanical super charging where-in a separate pump or blower or compressor (usually driven by the power taken from the engine) provides the compressed air. (ii) Turbo-Charging (a turbocharger) - where-in a compressor and turbine on a single shaft are used to boost the inlet air density. Energy available in the exhaust stream of the engine is utilized to drive the turbocharger and in-turn the Compressor which raises the air density into the engine cylinder. (iii) Turbo-compounding uses a a second turbine in the exhaust directly geared to the engine drive shaft. Out-of the three, turbo-charging is more effective in LHR Engines due to high exhaust gas temperatures.
Advantages of LHR Engine Decrease in Ignition Delay, Proportion of premixed combustion decreases while the proportion of late combustion increases. Extended duration of combustion duration hence uniform heat distribution Decreased heat release rate during the main stage of combustion Less increase in the cylinder pressure Increase in the temperature of working gases and exhaust gases Rise in mean temperature of cylinder walls. Lower SEC Increased life of the Engine Suitable for multi-he1 operation, particularly for Bio-diesels. 5.2.1 Emission from LHR Engine NOx emissions from the LHR Engines is generally higher than that of the conventional engines due to higher combustion temperature and longer combustion duration. Similarly the Hydrocarbons release rate is less at lower temperatures of working of the engine, but as the load increases on the engine, the temperature increases and also rise in Hydrocarbons. But the NOx emissions can be reduced by the usage of Bio-Diesel in DI Diesel Engines. Therefore, to better utilisation of the thermal energy inside the engine cylinder, various types of LHR Engines are being developed. Some of them are: (i) Ceramic coated Engines (ii) PSZ Coated Engines
(iii) (iv) (v) Air gap insulated piston engine Air Gap insulated piston and air gap insulated linear engine Air Gap insulated piston, air gap insulated linear engine with ceramic coated engine. As the heat resistant materials insulate the cylinder walls, the temperature would tend to rise particularly after working loads, leading to cooling issues and the release of exhaust gases to the atmosphere at high temperatures. Therefore, the Air -6 Gap insulated Piston Engines are preferred when cornparedcoated Engines. The main materials used for coatings are: Silicon Nitride, Silicon Carbide, Magnesia- PSZ, Chromium Oxide and other combinations with PSZ. Hence, to overcome such issues engine modifications, particularly the air gap insulated piston is being tried since it reduces the heat losses and also maintain uniform temperature. The detailed Literature on the LHR Engine is given in Para - 2.7 in Chapter - 2. 5.3 LHR ENGINE DEVELOPMENT The Piston Crown in the DI Diesel Engine on which the experiments are conducted as shown in Chapter-4 is replaced with Brass crown. A Brass piece machined to obtain the crown suitable so as to attach to the Piston. The Brass crown is attached such that an air gap could be provided. The Brass crown with its End View in Figure - 5.1; the Plan in Figure - 5.2 and the Assembly in Figure - 5.3 are shown. The cross section of the Piston Crown with air gap arrangement is shown in Figure - 5.4. Then the piston is set-up inside the engine cylinder.
5.4 METHODOLOGY OF EXPERIMENTS The Methodology starts with conducting experiments by using Diesel as he1 and the observations are recorded on-line for various pressures, 160, 180, 200, 220 and 240 bar in steps of 20 bar. Then the engine is run with the five better Bio-Diesel Blends (B30DH, B30JP, B30MH, B30NM and B2OPN) by following the Methodology explained in Chapter - 4. The experiments are conducted for the engine performance and some of the observations as sample are shown for pure Diesel at 200 bar Injection Pressure on LHR Engine, Table - 5.1, followed by the best blend B30DH at 200 bar Injection Pressure on the LHR Engine, Table - 5.2; and for all the best blends at 200 bar Injection Pressure on LHR Engine, Table - 5.3. The output results of Thermal Efficiency obtained with all the best combination of all the Bio-diesel blends from the conventional Diesel Engine in Figure - 5. 5 followed by the output from the LHR Engine, in Figure - 5.6 are shown in terms of Bar Charts.
Figure. 5.1: End view of the Crown (LHR)
~lumin'iurn Skirt Figure-5.2: Piston Assembly with Brass Crown (LHR) Figure-5.3: Top view of Crown (LHR) 143
Figure-5.4: Cross Section of the LHR Piston 5.5 SUMMARY The Methodology in the construction of the LHR Engine has been explained by modifications to the Aluminum piston. The Aluminum piston crown is replaced by a Brass Crown by air gap. Then the piston assembly is set inside the cylinder and closed, Later on the experiments are conducted on the LHR engine with Diesel and followed by Bio-diesel Blends of five non-edible oils. The observations are recorded for various Injection Pressures of 160, 180,200,220 and 240 bar. The Exhaust Gas Readings and Smoke Meter Readings are recorded for Analysis. The Results and Discussions are presented in the next Chapter.
Table-5.1: Experimental results for pure Diesel at 200 bar Injection Pressure on LHR Engine No* BP (KW) B.TH.E BSEC (KJ 1 KW-hr) COO/t HC ppm C02 % 0 2 % NOX ppm EGT O 1 0 0 ------- 0.069 19 2.58 17.55 62 140 2 0.746 10.42 38216 0.086 24 4.12 15.73 357 195 3 1.482 16.26 23591 0.087 35 5.73 13.46 549 220 4 2.201 20.14 18808 0.102 42 6.31 12.78 657 245 5 2.908 22.95 16400 0.116 50 7.32 11.24 723 275 6 3.618 25.32 14802 0.1 19 61 8.83 9.79 834 295 7 4.291 26.83 13420 1.034 73 9.53 8.19 1026 330 8 4.589 25.12 14002 1.132 74 9.56 8.01 1024 331
Table-5.2: Experimental Results for the best blend B30DH at 200 bar Injection Pressure on the LHR Engine S No. BP 0 B.Tl3.E BSEC (KJi KW-hr) CO% Hc ppm co2 O/o o2 % NOx PPm EGT (C) 1 0 0 ------- 0.047 15 3.5 17.47 40 120 2 0.746 11.18 37573 0.053 24 4.81 15.33 232 165 3 1.482 17.2 23073 0.32 33 5.75 13.1 401 195 4 2.201 21.28 18295 0.44 39 7.5 12.35 523 220 5 2.908 24.3 15859 0.056 41 7.96 11.1 1 639 250 6 3.618 26.9 14229 0.169 43 8.9 9.65 684 270 7 4.291 28.62 12577 0.325 48 9.8 7.99 732 285 8 4.574 27.21 13467 0.336 49 9.9 7.89 721 285
Table-5.3: Experimental observations for all best blends at 200 bar Injection Pressure on LHR Engine Oil Best Blend Best Injection Pressure (Bar) Max. B.TH.E. Minimum SEC(KJ1 KW-hr) Max. CO % Max, HC (ppm) Absorb. Coft. (K) Max. NOx (PP~) Max. ECT. (C) Diesel -- 200 26.83 13417 1.034 73 1.8 1026 330 Deccanhemp 30 200 28.62 12577 0.325 48 1.274 732 285 Jetropha 30 200 28.2 12765 0.523 62 1,461 920 322 Mahua 30 200 27.62 13034 0.428 54 1.02 871 305 Neem 30 200 26.73 13468 0.629 67 1.61 1 788 302 Pungamia 20 180 26.6 13533 0.742 70 1.942 828 310
. -- -.- Conventioal Engine Diesel PN 0 NM MH JP DH Bio-Diesel Blends Figure - 5.5 : Comparison of Thermal Efficiency of all the Bio-diesel Blends on Conventional Engine LHR Engine I Bio-Diesel Blends Figure - 5.6 : Comparison of Thermal Efficiency of all the Bio-diesel Blends on LHR Engine.