Diesel Engine Power Output Research Articles

Identification of power output of diesel engine by analysis of the vibration signal

Power output is one of the main working parameters of a diesel engine, which not only reflects its dynamic performance but also acts as an important indicator of its operating state. At present, diesel engine power monitoring mainly depends on dynamometers, but most engines cannot be so equipped during operation. In addition, other techniques, such as in-cylinder pressure measurements used to gauge power output are invasive and have higher requirements for sealing and reliability. Therefore, it is important to study other means for achieving real-time monitoring of engine power that do not damage the engine. In this paper, we use the vibration acceleration of the combustion phase in the angle domain as the original signal to identify the output power. However, the signal contains many interference signals and must be pre-processed by purification techniques such as filtering, de-noising and empirical mode decomposition. Finally, the automatic identification of the power of a diesel engine is realized by means of inductive monitoring system algorithms. The test results show that the recognition accuracy under the five different working loads ranges between 83% and 95%, which demonstrates the effectiveness of the proposed method.

Design, Modelling, and Control of a Waste Heat Recovery Unit for Heavy-Duty Truck Engines

This paper presents a feasibility study on a waste heat recovery system for heavy-duty truck engines based on organic Rankine cycle (ORC) technology. The elements of novelty of the work are: i) the proposed plant configuration, and ii) the feasibility study that encompasses the whole preliminary design workflow of the system, namely, from the thermodynamic cycle optimization and the components preliminary sizing, to dynamic modelling and the design of a PI-based control system. The conceived ORC turbogenerator employs hexamethyldisiloxane (MM) as working fluid and achieves a maximum rated mechanical power of approximately 5 kW at the design point, corresponding to a truck cruise speed and a Diesel engine power output of 85 km h-1 and 100 kW respectively. Regarding the dynamic performance, the higher response time of the ORC unit compared to that of the Diesel engine makes the adoption of an advanced control system necessary. In particular, the simulation of a PI-based control system shows that it becomes impossible to prevent the thermal decomposition of the working fluid when the engine operates continuously at high power levels. This case study demonstrates the importance for automotive ORC applications of performing the investigation of dynamic performance and control design already in the early design phase.

Performance Analysis of an Evaporator for a Diesel Engine–Organic Rankine Cycle (ORC) Combined System and Influence of Pressure Drop on the Diesel Engine Operating Characteristics

The main purpose of this research is to analyze the performance of an evaporator for the organic Rankine cycle (ORC) system and discuss the influence of the evaporator on the operating characteristics of diesel engine. A simulation model of fin-and-tube evaporator of the ORC system is established by using Fluent software. Then, the flow and heat transfer characteristics of the exhaust at the evaporator shell side are obtained, and then the performance of the fin-and-tube evaporator of the ORC system is analyzed based on the field synergy principle. The field synergy angle (β) is the intersection angle between the velocity vector and the temperature gradient. When the absolute values of velocity and temperature gradient are constant and β < 90°, heat transfer enhancement can be achieved with the decrease of the β. When the absolute values of velocity and temperature gradient are constant and β >90°, heat transfer enhancement can be achieved with the increase of the β. Subsequently, the influence of the evaporator of the ORC system on diesel engine performance is studied. A simulation model of the diesel engine is built by using GT–Power software under various operating conditions, and the variation tendency of engine power, torque, and brake specific fuel consumption (BSFC) are obtained. The variation tendency of the power output and BSFC of diesel engine–ORC combined system are obtained when the evaporation pressure ranges from 1.0 MPa to 3.5 MPa. Results show that the field synergy effect for the areas among the tube bundles of the evaporator main body and the field synergy effect for the areas among the fins on the windward side are satisfactory. However, the field synergy effect in the areas among the fins on the leeward side is weak. As a result of the pressure drop caused by the evaporator of the ORC system, the diesel engine power and torque decreases slightly, whereas the BSFC increases slightly with the increase of exhaust back pressure. With the increase of engine speed, power loss, torque loss, and BSFC increment increase gradually, where the most significant change is less than 1%. Compared with the diesel engine itself, the maximum increase of power output of the diesel engine–ORC combined system is 6.5% and the maximum decrease of BSFC is 6.1%.

Effect of oxygen enriched combustion and water–diesel emulsion on the performance and emissions of turbocharged diesel engine

Oxygen enriched combustion (OEC) is potential to improve emissions, thermal efficiency and brake power output of diesel engine. The purpose of this investigation is to study whether it is feasible to apply water diesel emulsion to mitigate the increasing NOx caused by OEC with comparable BSFC and power output. Effect of OEC on particle size and number concentration was also analyzed in this paper. Oxygen concentration of intake air varied from 21% to 24% by volume. Water content in tested fuels was 0%, 10%, 20%, and 30% by volume respectively. The result indicated that lower BSFC, higher cylinder pressure and shorter ignition delay were observed when OEC was applied, while opposite trends were found when using WDE. Reduction of PM and NOx can be realized simultaneously by applying OE combined with WDE. Particle number concentration of nucleation mode increases with increasing oxygen concentration, while that of accumulation mode decreases. Optimal operating condition was realized when water content in emulsion was below 20% along with low oxygen enrichment.

Experimental Study of Diesel Engine Cycle-to-Cycle Variation—Part III

Marine diesel engine excitation can occur from the cycle-to-cycle variation in the engine output. The cycle-to-cycle variation in maximum cylinder pressure (Pmax) is often used to represent this variation. Earlier studies examined the correlation between the cycle-to-cycle variation in the maximum cylinder pressure (Ρmax), pressure impulse (PI) and ignition delay (ID) for the case of constant injection setting. This paper summarizes the results of systematic experiments to determine the cycle-to-cycle variations when the injection timing is changed. In these tests the cycle-to-cycle variations in the maximum cylinder pressure (Pmax), ignition delay (ID), and corresponding pressure impulse (PI) are examined for a single-cylinder test diesel engine at various speeds and compression ratios. Comparisons show that the cycle-to-cycle variations of the diesel engine power output are strongly affected by the injection timing. The best parameter for describing the cycle-to-cycle output variation is shown to depend on the specific engine test condition.

Diesel engine waste-heat power cycle

This article demonstrates a possibility for increasing the power output from diesel engines and improving the fuel economy for such engines. This is achieved by employing a power cycle which is driven solely by the engine waste-heat in the cooling water and, also, the exhaust gases. For road engines an organic fluid Rankine cycle is employed. R-12 is evaporated in a boiler, fired by the coolant waste-heat. This is superheated using the exhaust-gases before it is introduced to a turbine where it expands down to an air-cooled condenser. The cycle power output can supplement the base engine power by about 16% of its output. For stationary diesel engines, however, water is used in a steam Brayton power cycle. The released steam, from the cooling water in a flashing chamber, is compressed by a vapour compressor and superheated by the exhaust-gases. This steam is admitted to a turbine coupled to the compressor and the balance of the shaft power is the net output from the cycle. This amounts to about 15·3% of the base engine output. The power cycles employed neither interfere with the operation of the base engine nor deny the application of a turbocharger to it. The thermodynamic analysis for the cycles is given, and the results show the potential for employing such cycles in order to improve the diesel engine's power output by up to 16%.