White Paper 00114 Tapio Pohjalainen +358 40 864 9224 tapio.pohjalainen@waulis.com
Abstract Trends in automotive industry for engine performance both in regulatory requirements and customer expectations are parallel; both requires less polluting and more miles per gallon. This can be achieved only by improving thermal efficiency of an engine. One of the most prospective avenues is variable compression ratio technology (VCR). VCR technology is known theory over decades within the industry but not yet has been commercially available. We study in this paper Waulis TM technology of producing a device able to optimize compression ratio in each cylinder individually giving best performance at any loading condition. Emphasis of Waulis TM VCR technology is on part load fuel efficiency but can also give a power boost. The system consists of a) eccentric gear at the bigger end of a connection rod. It is adjusting stroke length via an b) actuator and c) control gear combination. The system control parameter is measured with cylinder knocking sensor. 1. Introduction Waulis TM technology is suitable to both spark and compression ignitionas well as Diesel and HCCI. Our focus in this paper is on spark ignition engines at part load. Due to traffic and road safety conditions automobile engines are running most of the time at part load conditions. Engine power is adjusted controlling the air flow to cylinder and adjusting the fuel flow accordingly. This leads to a condition where we have less compressed air fuel mixture at the end of compression stroke. This is dramatically reducing the efficiency of the engine and we get less out of the fuel. Waulis TM improves this process significantly by its ability to increase compression ratio. In addition Waulis TM mechanism provides over expansion at the end of power stroke and thus less energy is wasted in form of exhaust gasses. Due to new engine kinematics piston movement downwards is faster than in traditional design. This will increase engine power as can be deduced form fundamental thermodynamic equation (1.1). (1.1) Coupled with variable valve timing we are able to benefit of Miller-cycle advantages. This all adds up to a capability of over 40% improvements in thermodynamic efficiency at part load conditions. 2. The system Great inventions are simple so is the Waulis TM concept. Previously attempts of producing Variable Compression Ratio have been heavy, clumsy and expensive. Waulis solution is on contrary light, simple and easy to manufacture with current production machinery, tooling and facilities. Only three parts are required, eccentric gear, control gear and adjusting actuator, see Figures 1.1 and 1.2. Page 2
Fig 1.1 Waulis TM system schematics Fig 1.2 System built in an engine 3. Waulis TM kinematics Waulis TM technology reprogram conventional internal combustion engine. This mechanical reprogramming is done by inserting two new variables to the system, amount of eccentricity and its phase angle in relation to camshaft angle (CA), which is automatically adjusted by engine control unit (ECU). Waulis system kinematics is in principle the same as the classic coupling of piston to cylinder. As we saw in Figures 1.1 and 1.2 there is one additional element between connection rod and crankshaft, namely the eccentric gear. By adjusting the position of the eccentricity we alter the effective stroke length. Also we should note that power stroke is geometrically different to induction. The same applies to compression and exhaust. In Figure 3.1 is plotted piston movement as per crank shaft (CA) position. The difference of WaulisTM (red) kinematics to traditional design (blue) is evident. Figure 3.1 Piston movement change when Waulis TM technology has been adapted as per CA Page 3
Figure 3.2 Different compression ratios and system kinematics Figure 3.3 Over Expansion Following markings are used when piston position equation is defined. Page 4
Piston position from center of crank shaft rotational axis is (3.1) 4. Measured and tested superiority Waulis Motors has built several concept engines. Latest tests at Oulu polytechnic have been analyzed and the result is that our concept has 29.1 % better thermodynamic performance than the engine prior to our modification, three small parts. Engine in comparison is currently in series production and is top of its class, non-charged 4-cylinders in line with 1.8 liter cubic capacity having in port fuel injection utilizing variable valve timing (VVT). In Figure 4.1 is shown measured pressure inside a cylinder. Both graphs represents engine speed 1500 RPM and same fuel flow. Page 5
Figure 4.1 Measured cylinder pressure, red is Waulis and blue is std engine. 5. Conclusions Waulis TM technology is on its way achieving the first stronghold to be accepted as a technology in internal combustion engines. This technology provides enhanced fuel efficiency and thus less emission. Both the engine power and torque increases proportionally. Due to the fact that engine compression ratio can be altered during engine run from 1:8 to 1:18 it is possible to use multiple fuels at their peak performance. Optimization may be either fuel economy, emissions or power depending on driving conditions. Quick adjustment, less than 20 ms, delivers instantaneous system response. Waulis TM provides the new engine generation in advent of more ecological means of transportation. Waulis is the bridge to the greener future. Page 6