scholarly journals The Szymkowiak’s over-expanded cycle in the rocker engine with the variable compression ratio – kinematics

2021 ◽  
Author(s):  
Stanisław Szwaja ◽  
Mirosław Szymkowiak
Keyword(s):  
Compression Ratio ◽  
Thermodynamic Cycle ◽  
Expansion Ratio ◽  
Exhaust Gas ◽  
Linkage Mechanism ◽  
Additional Element ◽  
Smooth Change ◽  
In The Beginning ◽  
Innovative Concept ◽  
Main Construction

The article discusses the innovative concept of the over-expanded thermodynamic cycle, the author of which is the Polish engineer-designer Mirosław Szymkowiak. This cycle is realized on the basis of a new and innovative, previously unknown design, of a piston-crankshaft linkage mechanism with the aid of an additional element known as a rocker arm. Additionally, the proposed mechanism allows for a smooth change of the compression/expansion ratio of the engine during its operation. In the beginning, the earlier conceptions of the rocker engine developed by Szymkowiak were presented, and then the main construction assumptions and kinematic calculations were described. It was confirmed, that the developed linkage has big potential in improving the engine's thermal efficiency by approximately 12% relative. Additionally, it significantly reduces the exhaust gas pressure, when the exhaust valve is opened, therefore, contributes to the reduction of the noise emitted by the engine.

scholarly journals A Theoretical Study on the Thermodynamic Cycle of Concept Engine with Miller Cycle

Processes ◽  
2021 ◽  
Vol 9 (6) ◽  
pp. 1051
Author(s):  
Jungmo Oh ◽  
Kichol Noh ◽  
Changhee Lee
Keyword(s):  
Compression Ratio ◽  
Thermal Efficiency ◽  
Engine Performance ◽  
Thermodynamic Cycle ◽  
Expansion Ratio ◽  
Boost Pressure ◽  
Miller Cycle ◽  
Compression Pressure ◽  
Air Mass ◽  
Atkinson Cycle

The Atkinson cycle, where expansion ratio is higher than the compression ratio, is one of the methods used to improve thermal efficiency of engines. Miller improved the Atkinson cycle by controlling the intake- or exhaust-valve closing timing, a technique which is called the Miller cycle. The Otto–Miller cycle can improve thermal efficiency and reduce NOx emission by reducing compression work; however, it must compensate for the compression pressure and maintain the intake air mass through an effective compression ratio or turbocharge. Hence, we performed thermodynamic cycle analysis with changes in the intake-valve closing timing for the Otto–Miller cycle and evaluated the engine performance and Miller timing through the resulting problems and solutions. When only the compression ratio was compensated, the theoretical thermal efficiency of the Otto–Miller cycle improved by approximately 18.8% compared to that of the Otto cycle. In terms of thermal efficiency, it is more advantageous to compensate only the compression ratio; however, when considering the output of the engine, it is advantageous to also compensate the boost pressure to maintain the intake air mass flow rate.

scholarly journals Improving Efficiency, Extending the Maximum Load Limit and Characterizing the Control-Related Problems Associated With Higher Loads in a 6-Cylinder Heavy-Duty Natural Gas Engine

2010 ◽  
Author(s):  
Mehrzad Kaiadi ◽  
Per Tunestal ◽  
Bengt Johansson
Keyword(s):  
Natural Gas ◽  
Compression Ratio ◽  
Diesel Engines ◽  
Maximum Load ◽  
Exhaust Gas ◽  
Gas Temperature ◽  
Heavy Duty ◽  
Load Limit ◽  
Overall Efficiency ◽  
Exhaust Gas Temperature

High EGR rates combined with turbocharging has been identified as a promising way to increase the maximum load and efficiency of heavy duty spark ignition Natural Gas engines. With stoichiometric conditions a three way catalyst can be used which means that regulated emissions can be kept at very low levels. Most of the heavy duty NG engines are diesel engines which are converted for SI operation. These engine’s components are in common with the diesel-engine which put limits on higher exhaust gas temperature. The engines have lower maximum load level than the corresponding diesel engines. This is mainly due to the lower density of NG, lower compression ratio and limits on knocking and also high exhaust gas temperature. They also have lower efficiency due to mainly the lower compression ratio and the throttling losses. However performing some modifications on the engines such as redesigning the engine’s piston in a way to achieve higher compression ratio and more turbulence, modifying EGR system and optimizing the turbocharging system will result in improving the overall efficiency and the maximum load limit of the engine. This paper presents the detailed information about the engine modifications which result in improving the overall efficiency and extending the maximum load of the engine. Control-related problems associated with the higher loads are also identified and appropriate solutions are suggested.

Quantification of knock benefits from reformate and cooled exhaust gas recirculation using a Livengood–Wu approach with detailed chemical kinetics

2016 ◽  
Vol 18 (7) ◽  
pp. 717-731 ◽  
Author(s):  
David K Marsh ◽  
Alexander K Voice
Keyword(s):  
Carbon Monoxide ◽  
Compression Ratio ◽  
Exhaust Gas Recirculation ◽  
Spark Ignition ◽  
Mitigation Strategies ◽  
Exhaust Gas ◽  
Spark Ignition Engines ◽  
Volume Percent ◽  
Hydroxy Radicals ◽  
Gas Recirculation

In this work, a simple methodology was implemented to predict the onset of knock in spark-ignition engines and quantify the benefits of two practical knock mitigation strategies: cooled exhaust gas recirculation and syngas blending. Based on the results of this study, both cooled exhaust gas recirculation and the presence of syngas constituents in the end-gas substantially improved the knock-limited compression ratio of the engine. At constant load, 25% exhaust gas recirculation increased the knock-limited compression ratio from 9.0 to 10.8:1 (0.07 compression ratio per 1% exhaust gas recirculation) due to lower end-gas temperature and reactant (fuel and oxygen) concentrations. At exhaust gas recirculation rates above 43%, higher intake temperature outweighed the benefits of lower end-gas reactant concentration. At constant intake temperature, cooled exhaust gas recirculation was significantly more effective at all exhaust gas recirculation rates (0.10 compression ratio per 1% exhaust gas recirculation), and no diminishing returns or optimum was observed. Both hydrogen and carbon monoxide were also predicted to improve knock by reducing end-gas reactivity, likely through the conversion of high-reactivity hydroxy-radicals to less reactive peroxy-radicals. Hydrogen increased the knock-limited compression ratio by 1.1 per volume percent added at constant energy content. Carbon monoxide was less effective, increasing the knock-limited compression ratio by 0.38 per volume percent added. Combining 25% cooled exhaust gas recirculation with reformate produced from rich combustion at an equivalence ratio of 1.3 resulted in a predicted increase in the knock-limited compression ratio of 3.5, which agreed well with the published experimental engine data. The results show the extent to which syngas blending and cooled exhaust gas recirculation each contribute separately to knock mitigation and demonstrate that both can be effective knock mitigation strategies. Together, these solutions have the potential to increase the compression ratio and efficiency of spark-ignition engines.

Effects of Exhaust Gas Recirculation on Knock Intensity of a Downsized Gasoline Spark Ignition Engine

2018 ◽  
Vol 141 (1) ◽  
Author(s):  
Mingzhang Pan ◽  
Haiqiao Wei ◽  
Dengquan Feng
Keyword(s):  
Compression Ratio ◽  
Fuel Injection ◽  
Maximum Amplitude ◽  
Exhaust Gas Recirculation ◽  
Spark Ignition Engine ◽  
Exhaust Gas ◽  
Engine Knock ◽  
Intake Pressure ◽  
Control Port ◽  
Gas Recirculation

Exhaust gas recirculation (EGR) has gained prominence as a significant method to control port fuel injection engine knock caused by high compression ratio and high intake pressure (IP). In this paper, the effect of EGR on knock intensity was investigated under various conditions which included different compression ratios (9:1, 10:1, 11:1), IPs (1.0 bar, 1.2 bar, 1.4 bar) and intake temperatures (ITs, 20 °C, 40 °C, 60 °C). The torque output being a crucial variant was also considered. The results showed that EGR effectively reduced the maximum amplitude of pressure oscillations (MAPO) and knock intensity factor (KI20). The effect of EGR on knock resistance was more significant at higher compression ratio, IP, and IT. The output torque of the engine reached a peak value with a suitable EGR ratio which also controlled the intensity of knock under different conditions.

Experimental Evaluation of Active Flow Control Mixed-Flow Turbine for Automotive Turbocharger Application

2005 ◽  
Author(s):  
Apostolos Pesiridis ◽  
Ricardo F. Martinez-Botas
Keyword(s):  
Flow Control ◽  
Pulse Pressure ◽  
Active Flow Control ◽  
Energy Levels ◽  
Expansion Ratio ◽  
Exhaust Gas ◽  
Potential Gain ◽  
Before And After ◽  
Pressure Peak ◽  
Active Flow

The current paper introduces a new concept in turbocharger development, namely, that of active turbocharger flow control. In the Active (Flow) Control Turbocharger (ACT) the nozzle is able to alter the inlet area at the throat of the turbine inlet casing in phase and at the same frequency as that of the incoming exhaust stream pulses. Actuated by an electrodynamic shaker the nozzle can adapt according to the engine exhaust gas pulse pressure variation, thus taking advantage of the lower energy levels existent before and after each pulse pressure peak, which the current systems do not take advantage of. Thus, ACT makes better use of the exhaust gas energy of the engine than a conventional VGT. The numerical simulation and experimental work concentrates on the potential gain in turbine expansion ratio and eventual power output as well as the corresponding effects on efficiency.

A Theoretical Study of a Variable Compression Ratio Turbocharged Diesel Engine

1992 ◽  
Vol 206 (4) ◽  
pp. 227-238 ◽  
Author(s):  
T J Rychter ◽  
A Teodorczyk ◽  
C R Stone ◽  
H J Leonard ◽  
N Ladommatos ◽  
...  
Keyword(s):  
Diesel Engine ◽  
Compression Ratio ◽  
Engine Performance ◽  
Expansion Ratio ◽  
Combustion Noise ◽  
Connecting Rod ◽  
Turbocharged Diesel Engine ◽  
Variable Compression Ratio ◽  
Engine Simulation ◽  
Variable Compression

A variable compression ratio concept that can give a different expansion ratio to the compression ratio has been evaluated by means of a simulation of a turbocharged diesel engine. The compression ratio is controlled by varying the ratio of the connecting rod length to the crank throw, hence the name variable crank radius/connecting rod length engine (VR/LE). The VR/LE mechanism kinematics have been defined and described, and the compression ratio and expansion ratio have been presented as a function of the eccentric phase angle (αo). A zero-dimensional engine simulation that has been the subject of comprehensive validation has been used as the basis of the VR/LE study. The effect of the compression ratio on the engine performance at fixed loads is presented. The principal benefits are a reduction in fuel consumption at part load of about 2 per cent and a reduction in ignition delay that leads to an estimated 6 dB reduction in combustion noise. The study has been conducted within the assumption of a maximum cylinder pressure of 160 bar.

Application of Over-Expansion Cycle to a Larger Gasoline Engine With Late-Closing of Intake Valves

2002 ◽  
Author(s):  
Seiichi Shiga ◽  
Kenji Nishida ◽  
Shizuo Yagi ◽  
Youichi Miyashita ◽  
Yoshiharu Yuzawa ◽  
...  
Keyword(s):  
Compression Ratio ◽  
Thermal Efficiency ◽  
Gasoline Engine ◽  
Engine Performance ◽  
Mechanical Efficiency ◽  
Expansion Ratio ◽  
Brake Thermal Efficiency ◽  
Gasoline Engines ◽  
Cylinder Test ◽  
Test Engine

This paper presents further investigation into the effect of over-expansion cycle with late-closing of intake valves on the engine performance in gasoline engines. A larger single-cylinder test engine with the stroke volume of 650 cc was used with four kinds of expansion ratio (geometrical compression ratio) from 10 to 25 and four sets of intake valve closure (I.V.C.) timings from 0 to 110 deg C.A. ABDC. Late-closing has an effect of decreasing the pumping work due to the reduction of intake vacuum, althogh higher expansion ratio increases the friction work due to the average cylinder pressure level. Combining the higher expansion ratio with the late-closing determines the mechanical efficiency on the basis of these two contrastive effects. The indicated thermal efficiency is mostly determined by the expansion ratio and little affected by the nominal compression ratio. The value of the indicated thermal efficiency reaches to 48% at most which is almost comparable with the value of diesel engines. The improvement of both indicated and brake thermal efficiency reaches to 16% which is much higher than ever reported by the authors. A simple thermodynamic calculation could successfully explain the behavior of the indicated thermal efficiency. The brake thermal efficiency could also be improved due to the increase in both mechanical and indicated efficiencies.

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