Gas turbine engine braking and method

A method of decelerating a ground vehicle driven by a gas turbine engine having a gas generator section and a free turbine output power section driven by a gas flow from the gas generator section, comprising the steps of:

• altering the incidence of gas flow from the gas generator section onto the free turbine section whereby said gas flow opposes rotation of the free turbine section;
• sensing the speeds of said gas generator and power turbine sections, and modifying the speed of said gas generator section to bring said sensed speeds within predetermined limits of one another;
• and
• subsequent to said altering and sensing steps, selectively mechanically interconnecting said gas generator and free turbine sections whereby the rotational inertia of the gas generator section tends to decelerate the free turbine section.

A method of providing deceleration for a ground vehicle driven by a gas turbine engine having a gas generator section producing gas flow to drive a free turbine power output section, comprising the steps of:

• increasing gas generator section speed;
• changing the incidence of gas flow from the gas generator onto the free turbine section to minimize power transferred to the free turbine section during said increasing step;
• and
• subsequently selectively mechanically interconnecting said gas generator and free turbine sections whereby the rotational inertia of the gas generator section tends to decelerate the free turbine section.

A method of providing deceleration for a ground vehicle driven by a gas turbine engine having a gas generator section producing gas flow to drive a free turbine power output section, comprising the steps of:

• sensing the speeds of said gas generator and power turbine sections;
• modifying the speed of said gas generator section to bring said sensed speeds within predetermined limits of one another;
• and
• subsequently selectively mechanically interconnecting said gas generator and free turbine sections whereby the rotational inertia of the gas generator section tends to decelerate the free turbine section.

A method of decelerating a ground vehicle driven by a gas turbine engine having a gas generator section and a free turbine power output section driven by gas flow from the gas generator section, comprising the steps of:

• reducing fuel flow to decrease gas generator section speed and reduce power transmitted to the power turbine section to provide a first mode of deceleration;
• altering the incidence of gas flow from the gas generator section onto the free turbine section so that said gas flow opposes rotation of the free turbine section to provide a second mode of deceleration;
• sensing the speeds of said gas generator and free turbine sections;
• and
• manually selecting a third mode of deceleration comprising the following steps:
• adjusting fuel flow to modify gas generator section speed to bring said gas generator and free turbine speeds within predetermined limits of one another;
• changing the incidence of gas flow onto the free turbine section to minimize power transferred to said free turbine section during said adjusting step,
• mechanically interconnecting said gas generator and free turbine sections once said speeds are within said predetermined limits,
• repeating said reducing fuel flow step and said altering step after said interconnecting step, and
• disconnecting said gas generator and free turbine sections once the speed of said gas generator section reduces to a preselected value.

A method of driving a power output shaft comprising the steps of:

• compressing an air flow;
• heating the compressed air in a combustor by delivering fuel to the combustor to support a combustion process therein;
• separately driving a first drive shaft and a second power output shaft by the gas exhausted from the combustor;
• utilizing power from the first drive shaft for said compressing step;
• sensing the speeds of said first and second shafts;
• and
• decelerating said second shaft by selectively controlling fuel flow delivered to the combustor to reduce the difference in said speeds to a preselected maximum, then mechanically interengaging said first and second shafts once said difference in speeds is less than said preselected maximum;
• and
• maintaining a continuous combustion process throughout said decelerating step.

In a gas turbine engine:

• compressor means for compressing gas flow;
• combustor means receiving gas flow from the compressor for heating said gas flow;
• means for delivering fuel to said combustor means;
• first and second turbine means driven by gas flow from said combustor;
• first shaft means operably interconnecting said compressor means and said first turbine means whereby said first turbine means drives said compressor means;
• second output shaft means operably coupled to be driven by said second turbine means;
• clutch means operably interposed between and selectively engageable to interconnect said first and second shaft means;
• means for sensing the difference in speeds of said first and second shaft means;
• and
• control means operably coupled with sensing means, said clutch means and said means for delivering fuel, said control means operable when activated to control fuel flow to said combustor to reduce said difference in speeds to a preselected maximum, and to engage said clutch means in response to reduction of the difference in speeds to said preselected maximum.

A gas turbine engine for driving a ground vehicle, comprising:

• a gas generator section;
• a free turbine power output section for driving said vehicle, said free turbine section arranged to be driven by gas flow from said gas generator section;
• means for altering the incidence of said gas flow onto said free turbine section whereby said gas flow opposes rotation of said vehicle;
• selectively actuatable means for mechanically interconnecting said gas generator and free turbine section whereby the rotational inertia of said gas generator section tends to decelerate the vehicle;
• means for delivering fuel flow to said generator section to maintain a combustion process therein;
• means for sensing the difference in speeds of said gas gas generator and free turbine sections;
• and
• control means operably coupled with sensing means, said selectively actuatable means and said means for delivering fuel, said control means operable when activated to control fuel flow to said combustor to reduce said difference in speeds to a preselected maximum, and to actuate said selectively actuatable means in response to reduction of the difference in speeds to said preselected maximum.

A gas turbine engine for driving a ground vehicle, comprising:

• a gas generator section;
• a free turbine power output section for driving said vehicle, said free turbine section arranged to be driven by gas flow from said gas generator section, and comprising a rotary turbine wheel having a plurality of turbine blades interposed in the stream of gas flow from said gas generator section;
• means for altering the incidence of said gas flow onto said free turbine section whereby said gas flow opposes rotation of said free turbine section and tends to decelerate said vehicle, and comprising a set of non-rotating, variable guide vanes disposed upstream of said turbine vanes, and means for adjusting the incidence of said guide vanes relative to said gas flow;
• means for selectively mechanically interconnecting said gas generator and free turbine section whereby the rotational inertia of said gas generator section tends to decelerate the vehicle, said interconnecting means comprising a clutch having power input and power output shafts, and first and second drive trains respectively operably interconnecting said power input shaft with said free turbine section, and said second drive train interconnecting said power output shaft with said gas generator section;
• means for delivering fuel flow to said gas generator section to maintain a combustion process therein;
• means for operably sensing the speeds of said input and output shafts of said clutch;
• and
• control means for energizing said clutch to interengage said input and said output shaft thereof, said control means including a manual selector switch, means responsive to said selector switch for adjusting fuel flow to said gas generator in response to said sensed input and output speeds to said clutch to adjust the speed of said gas generator section to bring said sensed speeds within predetermined limits of one another, and thereupon reduce fuel flow to the gas generator section to tend to decelerate the vehicle without interrupting the combustion process therein.

A gas turbine engine for driving a ground vehicle, comprising:

• a gas generator section;
• a free turbine power output section driven by gas flow from said gas generator section;
• clutch means having first and second shafts operably driven respectively by said free turbine section and said gas generator section;
• means for sensing the speeds of said first and second shafts;
• and
• control means for modifying the speed of said gas generator section to bring said sensed speeds within predetermined limits of one another, and to thereupon engage said clutch means to interconnect said first and second shafts.