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Method for Safe Engine Operation in Combination with a Grid Code Event

IP.com Disclosure Number: IPCOM000226875D
Publication Date: 2013-Apr-23
Document File: 3 page(s) / 164K

Publishing Venue

The IP.com Prior Art Database

Related People

Zimmermann Gilbert: CONTACT

Abstract

During a Grid Code event the IC-engine power suddenly drops from 100% load to 0% load and after about 100ms increases suddenly to 100%. For premix gas engines this is achieved by disabling the ignition. And for port injection engines by disabling the ignition and the gas admission. During a Grid Code event cold air (or air gas mixture in the case of premixed gas engines) is being pumped through the engine by the pistons, no combustion is taking place, and the exhaust gas at the turbine inlet decreases in pressure and temperature. As a result the turbine power is reduced and the compressor is not able to maintain the air/mixture flow at the prevailing intake receiver pressure. Under some engine operating conditions and engine intake manifold setups this may lead to compressor surging. Compressor surging is dangerous for the engine operation and especially for the turbocharger. Counter measures to avoid surging need to be taken. As Grid Code is a new requirement it is nowadays unknown how compressor surge is avoided by the engine builders.

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Safe engine operation in combination with the Grid Code Event

Method for Safe Engine Operation in Combination with the Grid Code Event

Invention Disclosure:

Method for Safe Engine Operation in Combination with a Grid Code Event

Background

During a Grid Code event the torque of the generator, powered by a turbocharged IC-engine, suddenly drops from 100% load to 0% load and after about 100 ms increases suddenly to 100%. Surging should be avoided to avoid emergency shut-down.

For premix gas engines this is achieved by disabling the ignition and for port injection engines by disabling the ignition and the gas admission.

During a Grid Code event cold air (or air gas mixture in the case of premixed gas engines) is being pumped through the engine by the pistons, no combustion is taking place, and the exhaust gas at the turbine inlet decreases in pressure and temperature. As a result the turbine power is reduced and the compressor is not able to maintain the air/mixture flow at the prevailing intake receiver pressure. .

Under some engine operating conditions this leads to compressor surging (see Figure 1).

Figure 1: Grid Code Transient Simulation Results

1



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Safe engine operation in combination with the Grid Code Event

Innovation

A) The exhaust gas temperature is increased with the purpose of providing more exhaust power to the tur- bocharger turbine without providing a significant power to the engine. This is achieved as follows:
 For premix gas engines the ignition occurs very late during the expansion phase. This minimizes or

disables completely the cylinder power and leads to very hot exhaust gas flowing into the exhaust receiver. The engine thermal load is not considered to be critical as only one cycle is powered as described, furthermore only few cylinders need to be fired as described, in fact the very high exhaust gas enthalpy is compensating the cold air coming by the other cylinders. If the Grid Code event lasts more than one cycle, the late firing can be switched between different cylinders.

 For port injection engines, the cylinders, for which a late firing is required, need to be admitted with gas. In the case of gas engines with a pilot spray type of ignition, and ignition timing needs to be se- lected such that an ignition of the pilot spray is still possible.

B) Shift the operating point in the compressor map by means of an engine control elements:
 A compressor circulation valve is able to react within few tens of milliseconds. A quick opening al-

lows shifting the operating point in the compressor map on the right without surging.

 Full opening of the throttle valve mitigates the risk of compressor surg...