Effect of gasoline homogeneous charge compression ignition on engine acoustics and vibration

Abstract

The homogeneous charge compression ignition (HCCI) gasoline engine promises low fuel consumption without expensive NO x aftertreatment. Owing to the self-ignition, HCCI has a faster combustion and therefore a higher level of vibration and acoustic excitation than DI-spark ignition (SI) engines. To effect a gasoline engine running in HCCI mode, residual gases must be trapped in the combustion chamber in HCCI mode. One solution to trap residual gases is to establish a negative valve timing overlap. This was done on a gasoline I4 engine, which is able to run in SI or HCCI mode by using independently controlled overhead camshafts. Noise and vibration analysis has been carried out on such an HCCI engine to quantify the impact of HCCI on the combustion and intake orifice noise. The noise and vibration analysis was done using either directly measured noise and vibrations from the development dynamometer or a noise prediction method based on recorded cylinder pressures and known transfer functions. The investigations were carried out at different speed and load points while changing control parameters such as intake cam timing, throttle, spark and injection timing and strategy. Using different data evaluation methods it was found that the HCCI mode with base settings can deliver higher NVH excitation than the SI mode at the same speed and load. However, by applying different combinations of control parameters, the NVH of the HCCI operation mode can be controlled in order to reduce its level of excitation and noise characteristics.

Impact of simple surge-enhancing inlet geometries on the acoustic behavior of a turbocompressor

“…As NVH issues of combustion-powered vehicles are becoming crucial for manufacturers due to customer and regulator requirements for quieter vehicles [7], especially taking into account the increased popularity of quieter electric vehicles, accounting for all sources of noise in the engine is a necessity.…”

Dynamic effects of the power-conversion module in a reciprocating engine

“…Moreover, Pye demonstrated on a gasoline engine that this effect takes place independently of the accompanying peak pressure [2]. Nowadays this issue is rather associated with compression ignition engines and, occasionally in the future, with the homogeneous charge compression ignition (HCCI) in gasoline engines [3,4]. The frequency range that cares for the annoying "impulsive" noise characteristics has been identified in the range of 0.5-3 kHz [3][4][5].…”

“…Nowadays this issue is rather associated with compression ignition engines and, occasionally in the future, with the homogeneous charge compression ignition (HCCI) in gasoline engines [3,4]. The frequency range that cares for the annoying "impulsive" noise characteristics has been identified in the range of 0.5-3 kHz [3][4][5]. A detailed research into the dynamic response of the power-conversion system gains more importance in the light of stringent emission legislations and limited latitudes of the control system in reducing the pressure rise rate of the combustion and thus the sharpness of the excitation.…”

On the impact of the pressure rise rate on piston and connecting rod dynamics in internal combustion engines

“…A comparison of the excitation mechanisms of CAI and SI revealed higher amplitudes of the combustion excitation when operating in CAI. Moreover, the CAI combustion delivers a significantly increased pressure rise rate of the cylinder pressure in parallel with a short burn duration compared with SI-operation [1]. At a first glance, this is obviously not a novel cause for the impulsiveness, because since the introduction of compression ignition (CI) engines research has been conducted to identify the sources of the impulsive noise characteristics especially at part-load conditions of such engines while studying the impact of the shape of the combustion pressure characteristics.…”

“…Note that combustion takes place around 23408 crank angle (ignition TDC): (a) Individual forced response of the considered eigenfrequencies; time response of the model, subjected to SI combustion (one cycle) and (b)Individual forced response of the considered eigenfrequencies; time response of the model, subjected to HCCI combustion (one cycle). The pressure peak around 19808 crank angle is caused by the precompression strategy to initiate HCCI operation[1]…”